firmware: ti_sci: rm: Remove unused config() from ti_sci_rm_ringacc_ops

The ringacc driver has been converted to use the new set_cfg function to
configure the ring, the old config ops can be removed.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>